WORKING DRAWINGS HANDBOOK, Fourth Edition

Drawing the set

probably the most common in general use but it is
arguable that 112 g/m^2 justifies its extra cost, being
dimensionally more stable and less liable to go brittle
with age.

Draughting filmis expensive but it is dimensionally
stable, takes ink and pencil well and both may be
erased easily. However, it is hard on the normal
technical pen and it is desirable to use a range with
specially hardened tips.

Ink and pencilare the two available media for
drawing lines and the choice rests to some extent
with the individual. Many find pencil the more
sympathetic medium, with its wide range of line
inflexions. The function of a working drawing,
however, is the unambiguous conveyance of drawn
information, and aesthetic considerations must remain
secondary.

Line thickness

Line thicknesses offered by the manufacturers of
technical pens cover a wide range. Figure 4.1shows
them at full size. It will be noted that there are two
ranges available, Range One being the most common
and Range Two based on German DIN standards. With
Range Two each size doubles the thickness alternately
preceding it, with the result that alterations may be
carried out to an enlarged or reduced copy negative in a
similar weight of line to that appearing on the original.
(This applies equally when manual alterations to CAD
printed drawings is being carried out.)

It is of course undesirable to mix the ranges on any
given drawing. For 1:2 reduction of negatives the
minimum recommended line thickness for use on the
original drawing is 0.25 mm, allowing the use of the
minimum size 0.13 mm pen for any alterations.

In any process of reduction the minimum line thickness
on the final print should not be less than 0.13 mm if

legibility and uniformity of reproduction are to be

maintained. But for the normal production of working

drawing negatives, where reproduction may be expected

to be at a 1:1 ratio, there is no reason why a thickness

of 0.18 or 0.2 should not be selected for the thinnest

line used.

Three different line thicknesses will suffice for most

drawings. If we term them (a), (b) and (c), with (a)

being the thinnest and (c) the thickest, the various

4.1 The range of line thicknesses available with the

use of technical pens